--建立表

CREATE TABLE userinfo3 (
    ID INT PRIMARY KEY NOT NULL, --ID 整數型別，設定為主鍵，並且不能為空
    name VARCHAR ( 10 ) NOT NULL, --name 可變長度字元型別，不能為空
age INT NULL --age 整數型別，可以為空 
)

--in子查詢 把子查詢select的結果當作主查詢的in 條件使用即可
SELECT * FROM userinfo3 WHERE age in (select age from userinfo2 WHERE isV = 1)
SELECT
 
 * FROM userinfo3 WHERE age not in (select age from userinfo2 WHERE isV = 1) --not in 反向

--查詢某一條件的區間條件
select * from userinfo3 where age BETWEEN 22 and 25


-- 查詢a表和b表中age欄位中相同的值，存在則顯示
SELECT a.id,a.name,a.age,a.sex from userinfo3 as a 
where exists(select * from userinfo2 as b where a.age = b.age);
 
-- 反,不存在顯示
SELECT a.id,a.name,a.age,a.sex from userinfo3 as a 
where not exists(select * from userinfo2 as b where a.age = b.age);

--查詢返回結果排序
--age倒序, id升序
select * from userinfo3 ORDER BY age DESC,id
--預設是=升序
select * from userinfo3 ORDER BY age,id ASC


--函式
select count(name) from userinfo3 WHERE
 
 age >= 23
select sum(age) from userinfo3